1. Field of the Invention
The present invention relates to movable body drive methods and movable body drive systems, pattern formation methods and apparatuses, exposure methods and apparatuses, and device manufacturing methods, and more particularly to a movable body drive method and a movable body drive system that drive a movable body within a moving plane, a pattern formation method using the movable body drive method and a pattern formation apparatus equipped with the movable body drive system, an exposure method using the movable body drive method and an exposure apparatus equipped with the movable body drive system, and a device manufacturing method using the pattern formation method.
2. Description of the Background Art
Conventionally, in a lithography process in the manufacturing of microdevices (electron devices or the like) such as semiconductor devices and liquid crystal display devices, exposure apparatuses such as a reduction projection exposure apparatus by a step-and-repeat method (a so-called stepper) and a reduction projection exposure apparatus by a step-and-scan method (a so-called scanning stepper (which is also called a scanner) are relatively frequently used.
In these types of exposure apparatuses, in order to transfer a pattern of a reticle (or mask) to a plurality of shot areas on a wafer, a wafer stage that holds the wafer is driven in XY two-dimensional directions by, for example, a linear motor or the like. In particular, in the case of the scanning stepper, not only the wafer stage but also a reticle stage is driven by a linear motor or the like in a scanning direction in a predetermined stroke. Generally, position measurement of the reticle stage or the wafer stage is performed using a laser interferometer whose measurement values have good stability for a long period and which has a high resolution.
However, more accurate position control has been required due to finer patterns to cope with higher integration of semiconductors, and recently the short-term fluctuation of the measurement values caused by variation in the temperature of the atmosphere on the beam optical path of the laser interferometer has been accounting for a large share of the overlay budget.
Meanwhile, as a measurement apparatus other than the laser interferometer to be used for position measurement of a stage, an encoder can be cited, but because the encoder uses scales and the scales lack mechanical long-term stability (due to drift of scale pitch, fixed position drift, thermal expansion, and the like), and therefore, the encoder suffers from the disadvantages of lacking the linearity of the measurement values and being inferior in the long-term stability, compared with the laser interferometer.
In view of the disadvantages of the laser interferometer and the encoder as described above, various types of apparatuses that measure the position of a stage using both a laser interferometer and an encoder (position detection sensor that uses a diffraction grating) have been proposed (refer to Kokai (Japanese Unexamined Patent Application Publications) No. 2002-151405 and No. 2004-101362, and the like).
Further, although a measurement resolution of a conventional encoder was inferior to that of an interferometer, recently encoders having the measurement resolution equal or superior to the laser interferometers have come out (e.g. refer to Kokai (Japanese Unexamined Patent Application Publication) No. 2005-308592 and the like), and the technique of combining the laser interferometer and the encoder has been gathering attention.
However, in the case position measurement within the moving plane of a wafer stage on which a scale (grating) is arranged is performed using an encoder head, for example, in an exposure apparatus, the accuracy of the grating is similar to that of a movable mirror without bending correction, and therefore from the viewpoint of accuracy, it is obvious that the result of the position measurement without any correction can hardly be used for the position setting. That is, correction in view of the accuracy error of the grating is required. Further, in actual, since a grating surface is not a complete plane and the error component due to the uneven surface of the grating surface is also included in a count value, this error component also needs to be corrected. Moreover, there is the inconvenience that the measurement error of the encoder occurs due to not only the scale (e.g. flatness of the grating surface, or grating formation error) but also a head unit (e.g. gradient of the head, or optical characteristics), a relative displacement of the head and the scale in directions different from a measurement direction in which the encoder measures the position of the wafer stage, or the like.